Matlab Standalone exe conditional statement not working

Hello,

i´m working on an image registration program which will be exported by the mcc comand. The program uses an extern library which should not be included in the exe. After creating a Proto-File from the .dll and .h file and exporting the .m file as an exe the function is not working anymore. After some tests i think i might found the problem. Inside the function is a conditional if/ifelse statement to choose an image registration method. It seems like the standalone exe just skips this part and therefore multiple variables are not declared. The program then stops with the error "variable not found". I tried to replace the if-else statement with a switch case but this does not work as well. So my question is why does the standalone skip the conditional statement? Or may it be another problem?

Thank for the help!

[Adam]

Have you tried doing the tedious, but still effective placing of output statements within the different parts of the code (specifically in the if-else and printing out what the program things the value is of the condition being tested by the if-else) and then use the log of the executable or running it from command line to see which of these statements appear, what they say etc?

Unfortunately this type of old-fashioned debugging is sometimes the best approach to finding problems in executables that don't exist in code run from within Matlab.

There is no reason for if-else statements not to be evaluated in an executable though.

[Fabian Lübbert]

Yes i tried it with the disp() command. When running it in the Matlab enviroment the right values are displayed. The exe does not write anything at all. I tried it again after removing the if-else condition and only using one specific method. The code then works fine (surprisingly).

[Adam]

Are you displaying what the condition is that should be evaluated by the if-else statement?

And is it actually an if-else or an if-elseif with the possibility of certain (unexpected) values not meeting either criteria?

[Fabian Lübbert]

The statement consists of for different if/elseif conditions:

if flag == 1 
  /code
elseif flag == 2
  /code
elseif flag == 3
  /code
elseif flag == 4
  /code 
end

The flag is set as an input parameter of the function (beside two others). The first two input arguments are strings (I validated the correct input the function uses them correctly). The flag itself is just a integer. I used the disp to write the value of the flag with different inputs ( 1 to 4) but there was no output at all. There is only an output when removing the if statement completely. To clarify: it does not work as well when the code looks like this:

if flag == 1
  /code
end

[Adam]

The only option then is that the flag is not actually precisely equal to any of those options, either because it is somehow being inaccurately represented as a double or because it is actually a string or because for some reason it doesn't exist at that point.

If there was no output from disp it suggests that for some reason the flag variable does not exist at that point, although I'd assume there would be an error in that case, assuming the disp is immediately before the if statement.

You could also test by adding an else to your statement to catch all other cases and put a sprintf to output the flag with many decimal places in the else block.

Answer 1

[Steven Lord]

From the original message:

"The flag is set as an input parameter of the function (beside two others). The first two input arguments are strings (I validated the correct input the function uses them correctly). The flag itself is just a integer."

From the documentation in the "Using a MATLAB File You Plan to Deploy" section:

"When running MATLAB files that use arguments that you also plan to deploy with MATLAB Compiler, keep the following in mind:

• The input arguments you pass to your executable from a system prompt will be received as character vector input. Thus, if you expect the data in a different format (for example, double), you must first convert the character vector input to the required format in your MATLAB code. For example, you can use str2num to convert the character vector input to numerical data."

The char vector '1' is not equal to the double value 1.

>> '1' == 1
ans =
  logical
   0

[Fabian Lübbert]

That did the trick. I should´ve guessed that... Thank you very much that totally made my day!